The technical scope of the present invention is that of pyrotechnic igniters, that is to say components enabling a pyrotechnic effect to be transmitted in a pyrotechnic train.
Igniters whose cartridge is at least partially made of a plastic material are known by patents EP600791 and EP711400.
These igniters are, for example, intended to activate a pyromechanism or else to ignite a gas generating composition in an automobile safety system.
Their external profile is thus of a globally cylindrical shape intended to co-operate with a matching cavity in the gas generator or in the pyromechanism. They also have a rim that acts as an abutment during assembly operations, such rim also providing sealing by acting as a bearing surface for an O-ring.
These igniter cartridges are generally made by injection or duplicate-moulding.
The disadvantage of such cartridges is that they are of a shape that is specific to a given gas generator or pyromechanism.
However, there are different types of gas generators and pyromechanisms are available on the market and the attachment interfaces for the igniters are not, at present, standardised.
It is thus essential for the igniter production line to be specially adapted for each customer""s order so as to carry out duplicate-moulding of specific dimensions.
This results in an increase in production costs.
The aim of the present invention is to propose an igniter as well as an assembly process for such an igniter that does not suffer from such drawbacks.
Thus the igniter according to the invention is of a structure that allows it to be inexpensively manufactured for a given external geometry.
The assembly process according to the invention also allows igniters that have various external dimensions to be inexpensively manufactured.
The process according to the invention also allows for the easy integration of electronic components providing complementary functions (electromagnetic or electrostatic protection, logic circuits, firing device . . . ).
Thanks to the invention, the inner part of the igniter is the same whatever the outer geometry of the whole component. It is therefore possible to mass produce the essential and a priori the most expensive part of the igniter, that is to say the cartridge enclosing the pyrotechnic composition as well as the ignition means.
The igniter is thereafter customised by being installed in a casing having the external dimensions required for a specific customer.
Thus the subject of the invention is a pyrotechnic igniter comprising at least one pyrotechnic composition placed inside a cartridge composed of a substantially cylindrical case extended by at least two pins, such igniter being characterised in that the cartridge is placed inside a casing formed by joining at least two shells, such casing delimiting an inner volume accommodating the cartridge.
The casing is advantageously formed by joining an upper shell, delimiting the inner volume accommodating the cartridge, and a lower shell, provided with holes to allow the cartridge pins to protrude.
The casing can be formed by joining an upper shell, delimiting the inner volume accommodating the cartridge, and a lower shell provided with holes allowing two electrodes to protrude, both pins and electrodes being connected to a circuit placed in the inner volume.
The circuit can be carried by a card arranged perpendicularly to the pins and electrodes.
The card can be housed in a bore arranged in the lower shell.
The circuit can alternatively be housed in the upper shell.
Advantageously, the circuit will incorporate at least one component providing protection with respect to electromagnetic and/or electrostatic discharges.
The circuit can incorporate at least one component to decode a firing signal.
According to one characteristic of the invention, the casing has an outer profile enabling it to be attached to a gas generator or pyromechanism.
The shells can be joined together by ultrasonic sealing.
A further subject of the invention is an assembly process for a pyrotechnic igniter that allows it to be adapted to a specific gas generator or pyromechanism, such process being characterised in that it comprises the following steps:
firstly, an igniter cartridge is manufactured incorporating a substantially cylindrical case extended by at least two pins,
secondly, at least one casing is manufactured that has an outer profile allowing it to be adapted to a specific gas generator or pyromechanism, such casing incorporating an upper shell and a lower shell, said shells delimiting an inner volume to accommodate the cartridge,
the cartridge is placed in the casing,
the two shells forming the casing are joined together.
According to one variant of the process, at least two casings can be manufactured, each having a different outer profile, and each incorporating an upper and lower shell, said shells delimiting an inner volume to accommodate the cartridge. In this case, a casing will be chosen that has an outer profile corresponding to the gas generator or pyromechanism to which the igniter is to be adapted. The cartridge will then be placed inside the casing thus selected, and finally the two casing shells will be joined together.
The igniter cartridge can be attached to an electronic circuit before being housed in the selected casing.